JP6702673B2 - Inversion metamorphic multijunction solar cell with multiple metamorphic layers - Google Patents

Description

The present invention relates to the field of multi-junction solar cells based on III-V semiconductor compounds and to manufacturing processes and devices for 5- and 6-junction solar cell structures containing metamorphic layers. Some embodiments of such devices are also known as inverted modified multijunction solar cells. More specifically, the present invention is based on the disclosure of European Patent Publication No. 2610924, the contents of which are incorporated herein by reference.

Solar power derived from photovoltaic cells, also called solar cells, has been provided primarily by silicon semiconductor technology. However, in the past few years, the mass production of multijunction solar cells of III-V compound semiconductors for space applications has accelerated the development of this technology not only for space applications but also for terrestrial solar power applications. Compared to silicon, III-V compound semiconductor multi-junction devices have greater conversion efficiency and generally higher radiation resistance, but tend to be more complex to manufacture. Various aspects of III-V compound semiconductor multi-junction solar cells are discussed in EP-A-2610924.

The structure of the inverted transformation solar cell based on the III-V compound semiconductor layer is described in M. W. Wanglas et al., "Lattice Mismatch Techniques for High-Performance III-V Photovoltaic Energy Converters" (January 3-7, 2005, 31st IEEE Photovoltaic Experts Meeting/Proceedings, IEEE Press, 2005). , Presenting important conceptual starting points for the future development of commercial high efficiency solar cells. However, the materials and structures for many different cell layers proposed and described in such references present many practical difficulties with the proper choice of materials and manufacturing steps.

For example, prior to the disclosure set forth in EP-A-2610924, the materials and manufacturing steps disclosed in the prior art include commercially viable inverted deformed solar using commercially established manufacturing processes. There have been various drawbacks and inconveniences in producing cells.

European Patent Publication No. 2610924 U.S. Patent Application No. 12/271,192 US Patent Application No. 12/047,944 US Patent Application No. 12/258,190 US Patent Application No. 12/023,772 US Patent Application No. 11/860,183

M. W. Wanglas et al., "Lattice Mismatch Techniques for High Performance III-V Photovoltaic Energy Converters", IEEE Press, 2005.

The invention relates to a multijunction solar cell as defined in claim 1 and a method as defined in claim 14. Some embodiments are defined in the dependent claims.

EP-A-2610924 describes a multi-junction solar cell utilizing two or more metamorphic layers. Reference may be made to paragraphs [0038]-[0064] of EP-A 2610924. For example, European Patent Publication No. 2610924 discloses an upper first solar subcell having a first band gap and its base-emitter junction being a homojunction, and a first band gap adjacent to the first solar subcell. A multi-junction solar cell including a second solar subcell having a smaller second forbidden band width and a third solar subcell having a third forbidden band smaller than the second forbidden band width adjacent to the second solar subcell. Enter. The first composition-graded intermediate layer is provided adjacent to the third solar subcell, and the first composition-graded intermediate layer layer has a fourth band gap that is larger than the third band gap. A fourth solar subcell is provided adjacent to the first compositionally graded intermediate layer, and the fourth subcell has a fifth forbidden band smaller than the third forbidden band width so that the fourth subcell is lattice mismatched to the third subcell. Has a band width. The second composition gradient intermediate layer is provided adjacent to the fourth solar subcell, the second composition gradient intermediate layer has a sixth forbidden band width larger than the fifth forbidden band width, and the lower fifth solar subcell has a second forbidden band. The lower fifth subcell has a seventh forbidden band width smaller than the fifth forbidden band width so that the fifth subcell is provided adjacent to the compositionally graded intermediate layer and has a lattice mismatch with the fourth subcell. ing. For example, EP-A-2610924 describes 5 and 6 junction solar cells and methods of forming them. The teachings of all of these are incorporated herein by reference.

In some embodiments, the bandgap of the first composition graded intermediate layer is substantially constant at about 1.6 eV and the bandgap of the second composition graded intermediate layer is substantially constant at about 1.1 eV. It is advantageous to have Additional aspects, advantages, and new features of the disclosure will be apparent to those skilled in the art from this disclosure, including the following detailed description, and the practice of this disclosure. Although the present disclosure is described below with respect to preferred embodiments, it should be understood that the present disclosure is not limited thereto. Those of ordinary skill in the art, having the benefit of the teachings herein, will appreciate additional applications, modifications, and other field embodiments within the scope of the disclosures disclosed and claimed herein, for which the disclosures can be utilized. Will do. Various multijunction solar cells to which the present invention is applicable and methods of making them are disclosed in EP-A-2610924.

The invention will be better and more fully understood by reference to the following detailed description when considered in conjunction with the following accompanying drawings.

FIG. 4 is a cross-sectional view of a solar cell of one embodiment of a multi-junction solar cell after an initial stage of manufacturing, including deposition of certain semiconductor layers on a growth substrate. FIG. 1B is a cross-sectional view of the solar cell of FIG. 1A after the next sequence of process steps. FIG. 2B is a cross-sectional view of the solar cell of FIG. 1B after the next sequence of process steps. FIG. 1C is a cross-sectional view of the solar cell of FIG. 1C after the next sequence of process steps. FIG. 2D is a cross-sectional view of the solar cell of FIG. 1D after the next process step. FIG. 1E is a cross-sectional view of the solar cell of FIG. 1E after the next process step of attaching a substitute substrate. 1F is a cross-sectional view of the solar cell of FIG. 1F after the next process step of removing the original substrate. FIG. 2C is another cross-sectional view of the solar cell of FIG. 1G with a surrogate substrate placed at the bottom of the figure. 1H is a cross-sectional view of the solar cell of FIG. 1H after the next process step of removing the buffer layer and etch stop layer from the top of the solar cell, leaving the backside metal contact layer and removing the surrogate substrate. Corresponding to FIG. 4 of EP 2610924, one aspect of the present disclosure showing a 6-junction solar cell utilizing three metamorphic layers after an initial stage of manufacture involving deposition of a particular semiconductor layer on a growth substrate. It is sectional drawing of the solar cell of embodiment. Corresponding to FIG. 3B of European Patent Publication No. 2610924, one aspect of the present disclosure showing a five-junction solar cell utilizing two metamorphic layers after an initial stage of manufacturing involving deposition of a particular semiconductor layer on a growth substrate. It is sectional drawing of the solar cell of embodiment. Corresponding to FIG. 3C of EP2610924, another embodiment of a five-junction solar cell utilizing two metamorphic layers is shown after an initial stage of manufacture involving deposition of a particular semiconductor layer on a growth substrate. 1 is a cross-sectional view of a solar cell according to an embodiment of the present disclosure. Corresponding to FIG. 5 of EP 2610924, one aspect of the disclosure showing a five-junction solar cell utilizing one metamorphic layer after an early stage of manufacture involving deposition of a particular semiconductor layer on a growth substrate. It is sectional drawing of the solar cell of embodiment. Corresponding to FIG. 6 of EP-A 2610924, one of the present disclosure showing a 6-junction solar cell utilizing two metamorphic layers after an initial stage of manufacture involving deposition of a particular semiconductor layer on a growth substrate. It is sectional drawing of the solar cell of embodiment. 3 is a graph showing a combination of bandgap versus cell conversion efficiency for a multi-junction solar cell device that includes two compositionally graded interlayers, each having a substantially constant bandgap.

Reference is also made to European Patent Publication No. 2610924, FIGS. 1, 3A-3C and 5-25, and related documents.

(Glossary)
"III-V compound semiconductor" refers to a compound semiconductor formed using at least one element from Group III of the Periodic Table and at least one element from Group V of the Periodic Table. Group III-V compound semiconductors include binary, ternary and quaternary compounds. Group III includes boron (B), aluminum (Al), gallium (Ga), indium (In) and thallium (T). Group V includes nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb) and bismuth (Bi).

"Forbidden band width" refers to the energy difference (eg, in electron volts (eV)) that separates the top of the valence band and the bottom of the conduction band of a semiconductor material.

“Compound semiconductor” refers to a semiconductor formed using two or more chemical elements.

Compositionally graded interlayer-see "metamorphic layer".

An "inverted metamorphic multijunction solar cell" or "IMM solar cell" is a higher forbidden band subcell, a lower forbidden band, which is the "top" subcell that normally faces solar radiation in its final configuration. Refers to a solar cell in which the subcells are deposited or grown in "reverse" order on a substrate for deposition or growth on a growth substrate prior to deposition or growth of width subcells.

"Layer" refers to a relatively flat sheet or film of semiconductor or other material. Layers may be deposited or grown, for example by epitaxial or other techniques

"Lattice mismatch" refers to two adjacently placed materials that have different lattice constants.

"Metamorphic layer" or "compositionally graded intermediate layer" refers to a layer that generally achieves a gradual transition in lattice constant throughout its thickness in a semiconductor structure.

“Multijunction solar cell” refers to a solar cell that includes two or more discrete and distinct pn junctions, each of which can be tuned to a different wavelength of light.

The details of the invention are described below, including exemplary aspects and embodiments.

The basic idea of manufacturing an inverted metamorphic multijunction (IMM) solar cell is to grow the subcells of the solar cell in "reverse" order on a substrate. That is, a high forbidden bandwidth subcell (ie, a subcell having a forbidden bandwidth in the 1.8 to 2.2 eV range), which is the "top" subcell that normally faces solar radiation, is formed into a semiconductor such as GaAs or Ge. It is grown epitaxially on a growth substrate so that the subcells are lattice matched to such a substrate. One or more lower bandgap middle subcells (ie, having a bandgap in the 1.2 to 1.8 eV range) can then be grown on the higher bandgap subcells.

At least one lower subcell is substantially lattice-mismatched to the growth substrate, and the at least one lower subcell has a third lower bandgap (ie, 0.7-1.2 eV range). A forbidden band width of at least one lower sub-cell is formed on the middle cell. Thereafter, a surrogate substrate or support structure is deposited or provided on the "bottom" subcell or substantially lattice-mismatched lower subcell to substantially remove the growth semiconductor substrate. (The growth substrate can then be subsequently reused for growth of the second and subsequent solar cells.)

FIG. 1 of EP 2610924 is a graph showing the forbidden band width of a particular binary material and its lattice constant. This figure and the associated description are hereby incorporated by reference. To provide a suitable background, FIGS. 1A-1H generally show a series of steps for forming a four-junction solar cell, which is the parent application filed Nov. 14, 2008, US patent application. No. 12/271,192, which is incorporated herein by reference.

As described in EP-A-2610924, FIG. 1A depicts the sequential formation of three subcells A, B and C on a GaAs growth substrate. In particular, substrate 101 is shown, which is preferably gallium arsenide (GaAs), but may be germanium (Ge) or another suitable material. For GaAs, the substrate is preferably a 15 degree off-cut substrate, that is, its surface has (as described more fully in US patent application Ser. No. 12/047,944, filed Mar. 13, 2008). It is oriented 15 degrees from the (100) plane to the (111)A plane.

In the case of a Ge substrate, a nucleation layer (not shown) is deposited directly on the substrate 101. A buffer layer 102 and an etch stop layer are further deposited on the substrate or on the nucleation layer (for Ge substrates). In the case of a GaAs substrate, buffer layer 102 is preferably GaAs. In the case of a Ge substrate, the buffer layer 102 is preferably GaInAs. Thereafter, a GaAs contact layer 104 is deposited on the layer 103 and an AlInP window layer 105 is deposited on the contact layer. Subcell A consisting of n+ emitter layer 106 and p-type base layer 107 is then epitaxially deposited on window layer 105. Subcell A is generally lattice matched to growth substrate 101.

It should be noted that the structure of the multi-junction solar cell can be formed by any suitable combination of groups III-V listed in the Periodic Table, subject to the requirements of lattice constant and band gap. .. Here, the group III includes boron (B), aluminum (Al), gallium (Ga), indium (In), and thallium (T). Group IV includes carbon (C), silicon (Si), germanium (Ge), and tin (Sn). Group V includes nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi).

In one embodiment, the emitter layer 106 is composed of GaInP and the base layer 107 is composed of AlGaInP. More generally, in some embodiments, the base-emitter junction can be a heterojunction. In another embodiment, the base layer may be composed of (Al)GaInP, where the aluminum or Al terms in parentheses in the above formula are meant to be optional components, In this example, it can be used in an amount ranging from 0% to 30%. The doping profile of the emitter layer 106 and the base layer 107 according to the invention can be as described there in combination with FIG. 20 of EP 2610924.

In some embodiments, the band gap of base layer 107 is 1.91 eV or greater.

Subcell A will ultimately become the "top" subcell of the inverted deformed structure after completion of the process steps according to the invention described below.

A back surface field (“BSF”) layer 108, preferably p+AlGaInP, is deposited on top of the base layer 107 and is used to reduce recombination losses.

The BSF layer 108 drives minority carriers out of the region near the base/BSF interface to minimize the effects of recombination loss. In other words, the BSF layer 108 reduces recombination losses at the back surface of the solar cell subcell A, thereby reducing recombination at the base.

Deposition of successive heavily doped p-type and n-type layers 109a and 109b on top of the BSF layer 108, forming a tunnel diode, an ohmic circuit element forming the electrical connection between subcell A and subcell B. To do. Layer 109a is preferably composed of p++AlGaAs and layer 109b is preferably composed of n++GaInP.

A window layer 110 is deposited on top of the tunnel diode layer 109, preferably n+GaInP. The advantage of using GaInP as the material component of the window layer 110 is that GaInP is adjacent to the emitter layer 111, as more fully described in the co-pending patent application serial number 12/258,190 filed October 24, 2008. That is, it has a refractive index almost equal to. The window layer 110 used in subcell B also acts to reduce interfacial recombination losses. It will be apparent to those skilled in the art that additional layers can be added or removed from the cell structure without departing from the scope of this disclosure.

On the window layer 110, the n-type emitter layer 111 and the p-type base layer 112 of the layer of the subcell B are deposited. These layers are preferably GaInP and GaIn _0.0015 As (for a Ge substrate or growth template), respectively, or GaInP and GaAs (for a GaAs substrate), respectively, but any layer consistent with lattice constant and bandgap requirements. Other suitable materials for can be used as well. Thus, the subcell B may be composed of an emitter region of GaAs, GaInP, GaInAs, GaAsSb, or GaInAsN and a base region of GaAs, GaInAs, GaAsSb, or GaInAsN. The doping profile of layers 111 and 112 according to the present disclosure may be as described therein in conjunction with FIG. 20B of EP 2610924.

In some previously disclosed inverted deformed solar cell examples, the middle cell was a homostructure. In some embodiments of the present disclosure, similar to the structure disclosed in US patent application Ser. No. 12/023,772, the middle subcell is a heterostructure with a GaInP emitter with its window layer changed from AlInP to GaInP. There is. This modification eliminates the refractive index discontinuity at the window/emitter interface of the middle subcell, as more fully described in US patent application Ser. No. 12/258,190, filed October 24, 2008. In addition, the window layer 110 is preferably doped to be three times as concentrated as the emitter 111 to bring the Fermi level closer to the conduction band, resulting in band bending at the window/emitter interface and confining minority carriers to the emitter layer. become.

In one embodiment of the present disclosure, the middle subcell's emitter has a bandgap equal to that of the top subcell's emitter, and the third subcell's emitter has a bandgap greater than that of the middle subcell's base. Therefore, neither the emitter of the middle subcell B nor the emitter of the third subcell C is exposed to the radiable light that can be absorbed during the implementation and operation after the solar cell is manufactured. Nearly all of the photons representing the absorbable radiation will be absorbed by the bases of cells B and C, which have a narrower bandgap than the emitter. Therefore, the advantages of using a heterojunction subcell are (i) an improved short wavelength response to both subcells, and (ii) a large portion of the emitted light is more efficiently absorbed, resulting in a narrow bandgap. It is to be collected in the base. This action increases the short circuit current J _SC .

A BSF layer 113 having the same function as the BSF layer 109 is deposited on the cell B. P++/n++ tunnel diode layers 114a and 114b are respectively deposited on the BSF layer 113 in the same manner as layers 109a and 109b to form ohmic circuit elements to connect subcell B to subcell C. Layer 114a may be composed of p++AlGaAs and layer 114b may be composed of n++GaAs or GaInP.

In some embodiments, the barrier layer 115 is composed of n-type (Al)GaInP and is deposited on the tunnel diodes 114a/114b to a thickness of about 0.5 μm. Such barrier layers are intended to prevent propagation of threading dislocations into the middle subcell B and top subcell C in the opposite growth direction or into the bottom subcell A in the growth direction, 2007. See co-pending US patent application Ser. No. 11/860,183, filed Sep. 24, with details.

A metamorphic layer (or compositionally graded intermediate layer) 116 is deposited on the barrier layer 115. Layer 116 preferably comprises a monotonically varying lattice constant, preferably compositionally, so as to achieve a gradual transition of the lattice constant from subcell B to subcell C in the semiconductor structure while minimizing the occurrence of threading dislocations. It is a series of AlGaInAs layers with a stepwise slope. In some embodiments, the compositionally graded intermediate layer is composed of (In _x Ga _1-x ) _y Al _1-y As, but the intermediate layer band gap is substantially constant at or about 1 eV. Select x and y to stay at .6 eV (eg, in the range of 1.55 eV to 1.65 eV).

In the inverted metamorphic structure described in the Wanrath et al., supra, the metamorphic layer consists of 9 compositionally graded GaInP steps, each step layer having a thickness of 0.25 μm. As a result, each layer of Wanglas et al. has a different bandgap. In some embodiments, layer 116 comprises multiple layers of AlGaInAs, with monotonically varying lattice constants and each layer having the same bandgap of approximately 1.6 eV.

The advantage of utilizing a constant bandgap material such as AlGaInAs is that arsenic-based semiconductor materials are much easier to process than materials incorporating phosphorus from a manufacturing point of view in standard commercial MOCVD reactors. However, the small amount of aluminum in the bandgap material ensures the radiant transparency of the metamorphic layer.

Although one embodiment of the present disclosure utilizes multiple layers of AlGaInAs for the metamorphic layer 116 for manufacturability and radiant transparency, another embodiment of the present disclosure changes the lattice constant from subcell B to subcell C. Different material systems may be used for this purpose. Other embodiments of the present disclosure may utilize a continuously graded material as opposed to a stepped ramp. More generally, the compositionally graded interlayer has an in-plane lattice constant greater than or equal to the second solar cell, less than or equal to the third solar cell, and a greater bandgap energy than the second solar cell. It may be composed of any of As, P, N, and Sb-based III-V group compound semiconductors under the constraint of having it.

In another embodiment of the present disclosure, an optional second barrier layer may be deposited on the AlGaInAs metamorphic layer 116. The second barrier layer 117 will normally have a different composition than the barrier layer 115 and essentially performs the same function of blocking the propagation of threading dislocations. In one embodiment, barrier layer 117 is n+ type GaInP.

A window layer 118, preferably made of n+ type GaInP, is then deposited on the barrier layer 117 (or directly on the layer 116 if there is no second barrier layer). This window layer acts to reduce the recombination loss in subcell "C". It will be apparent to those skilled in the art that additional layers can be added or removed from the cell structure without departing from the scope of this disclosure.

On top of the window layer 118, the cell C layer, the n+ emitter layer 119 and the p-type base layer 120 are deposited. These layers are preferably n+ GaInAs and p+ GaInAs, or n+ GaInP and pGaInAs in the case of a heterojunction subcell, respectively, but are consistent with lattice constant and bandgap requirements. Other suitable materials can be used as well. The doping profiles of layers 119 and 120 are discussed in European Patent Publication No. 2610924 with respect to FIG. 20 thereof.

A BSF layer 121, preferably composed of AlGaInAs, is then deposited on top of cell C, which BSF layer performs the same function as BSF layers 108 and 113.

The p++/n++ tunnel diode layers 122a and 122b are respectively deposited on the BSF layer 121 in the same manner as layers 114a and 114b to form ohmic circuit elements to connect subcell C to subcell D. The layer 122a is composed of p++AlGaInAs, and the layer 122b is composed of n++GaInP.

FIG. 1B shows a cross-sectional view of the solar cell of FIG. 1A after the next sequence of process steps. In some embodiments, the barrier layer 123 is preferably composed of n-type GaInP and is deposited on the tunnel diodes 122a/122b to a thickness of about 0.510 μm. It is intended that such barrier layers prevent threading dislocations from propagating into the top and middle subcells A, B and C in opposite directions of growth or into subcell D in the direction of growth. , Co-pending US patent application Ser. No. 11/860,13, filed Sep. 24, 2007.

A metamorphic layer (or compositionally graded intermediate layer) 124 is deposited on the barrier layer 123. Layer 124 preferably comprises a monotonically varying lattice constant, preferably compositionally, so as to achieve a gradual transition of the lattice constant from subcell C to subcell D in the semiconductor structure while minimizing the occurrence of threading dislocations. It is a series of AlGaInAs layers with a stepwise slope. The bandgap of layer 124 is constant throughout its thickness and is preferably equal to approximately 1.1 eV. One embodiment of the compositionally graded intermediate layer can be described as being composed of (In _x Ga _1-x ) _y Al _1-y As, but with a constant band gap of approximately 1.1 eV. Select x and y as is. Advantageously, the bandgap of the first compositionally graded intermediate layer 116 is substantially constant at about 1.6 eV and the bandgap of the second compositionally graded intermediate layer is substantially constant at about 1.1 eV.

A window layer 125, preferably composed of n+ type AlGaInAs, is then subsequently deposited on layer 124 (or on another barrier layer, if one is located on layer 124). .. This window layer acts to reduce recombination losses in the fourth subcell “D.” Additional layers may be added to or removed from the cell structure without departing from the scope of this disclosure. It will be apparent to those skilled in the art that it is possible.

FIG. 1C shows a cross-sectional view of the solar cell of FIG. 1B after the next sequence of process steps. The cell D layer, the n+ emitter layer 126, and the p-type base layer 127 are deposited on the window layer 125. The layers are preferably n+ type GaInAs and p type GaInAs, respectively, although other suitable materials consistent with lattice constant and bandgap requirements can be used as well. The doping profile of layers 126 and 127 may be as discussed in connection with FIG. 20 thereof in EP 2610924.

Referring now to FIG. 1D, a BSF layer 128, preferably composed of p+ type AlGaInAs, is then deposited on top of cell D, the BSF layer performing the same function as BSF layers 108, 113 and 121.

Finally, a high bandgap contact layer 129, preferably composed of p++ AlGaInAs, is deposited on the BSF layer 128.

The structure of this contact layer 129 placed on the bottom (non-illuminated) side of the photovoltaic cell with the lowest forbidden band width of the multijunction photovoltaic cell (ie, subcell “D” in the illustrated embodiment) is shown. , And can be made to reduce the absorption of light passing through the cell, so that (i) the back surface ohmic metal contact layer under the contact layer 129 (non-irradiation side) also functions as a mirror layer, ( ii) It is not necessary to selectively etch away this contact layer to prevent absorption.

It will be apparent to those skilled in the art that additional layers can be added or removed from the cell structure without departing from the scope of this disclosure.

FIG. 1E is a cross-sectional view of the solar cell of FIG. 1D after the next process step, with metal contact layer 130 deposited on p+ semiconductor contact layer 129. The metal is a series of metal layers Ti/Au/Ag/Au.

Further, the selected metal contact configuration is one that has a flat interface with the semiconductor after heat treatment to activate the ohmic contacts. This means that (1) a dielectric layer that separates the metal from the semiconductor does not need to be deposited and selectively etched in the metal contact region, (2) the contact layer is specular over the wavelength range of interest. , To do so.

FIG. 1F is a cross-sectional view of the solar cell of FIG. 1E after the next process step, with an adhesion layer 131 deposited on the metal layer 130. The adhesive can be CR200 (manufactured by Brewer Science, Inc., Rolla, MO, USA).

In the next process step, a surrogate substrate 132, preferably sapphire, is deposited. Alternatively, the surrogate substrate can be GaAs, Ge or Si, or another suitable material. The surrogate substrate has a thickness of about 40 mil and is perforated with holes of about 1 mm diameter at 4 mm intervals to aid in subsequent removal of adhesive and substrate. Of course, substitute substrates with different thicknesses and perforation configurations could be used as well. Instead of using an adhesive layer 131, a suitable substrate (eg, GaAs) can be eutectic or permanently bonded to the metal layer 130.

FIG. 1G is a cross-sectional view of the solar cell of FIG. 1F after the next process step, which in one embodiment removes the original substrate by a series of lapping and/or etching steps that remove substrate 101 and buffer layer 103. The choice of a particular etchant depends on the growth substrate.

As mentioned above, in some embodiments, the band gap of the first composition graded intermediate layer 116 is approximately 1.6 eV (ie, within 1.6 eV±3% or about 1.55 to 1.65 eV). It is particularly advantageous that the forbidden band width of the second composition gradient intermediate layer 124 is substantially constant at about 1.1 eV (that is, in the range of 1.05 to 1.15 eV). Is.

Multiple 4-junction IMM solar cell devices, each device including two different graded intermediate layers, were fabricated by an IMM growth process. The device comprises the following semiconductor layers deposited on one another: a GaInP ₂ upper solar subcell (A) with a 1.9 eV bandgap and a GaAs second upper solar subcell (B) with a 1.41 eV bandgap. ), a first compositionally graded intermediate layer of InGaAlAs under the second subcell, a third solar subcell (C) of In _0.285 Ga _0.715 As with a forbidden band width of 1.02 eV, and a third InGaAlAs layer under the third subcell. It included a two-composition graded intermediate layer and an In _0.57 Ga _0.43 As lower solar subcell (D) having a bandgap of 0.67 eV. The device included a GaAs substrate having a bandgap of 1.41 eV. In each sample, the forbidden band width of the first composition graded intermediate layer was substantially constant at about 1.4 eV, 1.5 eV or 1.6 eV, while the forbidden band width of the second composition graded intermediate layer was substantially constant. Was substantially constant at about 1.0 eV, 1.1 eV or 1.2 eV. The higher bandgap composition-graded intermediate layer is disposed between the 1.41 eV junction and the 1.02 eV junction, and the lower bandgap composition-graded intermediate layer is formed with the 1.02 eV junction. It was placed between the junction of 67 eV. A solar cell having the following combinations of forbidden band widths was processed into a working element.

Cell performance was measured and cell conversion efficiency was calculated as shown in FIG.

The optimum combination of the forbidden band widths for the first and second compositionally graded intermediate layers is such that the forbidden band width of the first compositionally graded intermediate layer is in the range of about 1.5eV-1.6eV and The comparative test data in FIG. 3 shows that it occurs when the forbidden band width is approximately 1.1 eV (ie, the combination identifiers 5 and 6). These particular combinations of bandgap provide a relatively large increase in conversion efficiency. This is particularly advantageous in the field of solar cell devices where even a small improvement in conversion efficiency is generally considered important. What is particularly surprising is that the conversion efficiency obtained for a device in which the first compositionally graded intermediate layer has a bandgap of 1.6 eV and the second compositionally graded intermediate layer has a bandgap of 1.1 eV. It is a major improvement. The combination of 1.6 eV and 1.1 eV forbidden band widths for the compositionally graded interlayer may be advantageous for 5-junction and 6-junction devices as well as 4-junction devices. In general, it is advantageous for the first composition graded intermediate layer to have a bandgap of 1.6 eV (±3%) and the second composition graded intermediate layer to have a bandgap of 1.1 eV (±3%). There are cases.

In some embodiments, a method of forming a specific one of the compositionally graded intermediate layers includes selecting an intermediate layer composed of InGaAlAs and a chemical formula (In defined by a specific value of x and y). _x Ga _1-x ) _y Al _1-y As identifying a set of compositions, where 0<x<1 and 0<y<1, each composition having the same specific inhibition. It has a band width (for example, a specific value within the range of 1.6 eV (±3%) for the first composition gradient intermediate layer, or 1.1 eV (±3% for the second composition gradient intermediate layer). %) A specific value within the range). The method of forming a particular compositionally graded intermediate layer may also include the step of identifying the appropriate lattice constants on both sides of the compositionally graded intermediate layer such that they are matched to their respective adjacent solar subcells. The method of forming a specific compositionally graded intermediate layer further includes a composition of formula (In _x Ga _1-x ) _y Al _1-y As having a specific band gap defined by specific values of x and y. May be included, where 0<x<1 and 0<y<1, where the subset of compositions are matched to the solar subcells on one side of the compositionally graded interlayer. From the defined lattice constant to the specified lattice constant that matches the solar subcell on the opposite side of the compositionally graded interlayer.

In some cases, one or more steps may be performed by a computer program. For example, a collection of the formula defined by a particular value of x and _{y (In x Ga 1-x} ) composition of _y Al _1-y As, the composition same specific bandgap (e.g., The step of identifying a set of compositions having a specific value in the range of 1.6 eV±3%) may include utilizing a computer program. Similarly, the formula defined by a particular value of x and y be a subset of (In _x Ga _1-x) composition of _y Al _1-y As, the composition subset of compositionally graded intermediate layer Identify a subset of compositions with lattice constants that range from a specified lattice constant that matches the solar subcell on one side to a specified lattice constant that matches the solar subcell on the opposite side of the compositionally graded interlayer The step of performing may include utilizing a computer program.

This manufacturing method precisely controls the mole fraction of each of In, Ga and Al to form a compositionally graded intermediate layer as the first, second or other compositionally graded intermediate layer, and gradually increases it. Adjustment step can be included. A method of forming a particular one of compositionally graded interlayers also provides a metal-organic chemical vapor deposition (MOCVD) apparatus configured to independently control the flow rates of source gases of gallium, indium, aluminum and arsenic. And a step of forming a continuously compositionally graded intermediate layer as a specific compositionally graded intermediate layer by selecting a reaction time, a temperature, and a flow rate ratio to each source gas.

FIG. 1H is a cross-sectional view of the solar cell of FIG. 1G with the substitute substrate 132 oriented such that it is at the bottom of the figure.

FIG. 1I is a cross-sectional view of the solar cell of FIG. 1H after the next process step of removing the buffer layer and the etch stop layer from the top of the solar cell, leaving the backside metal contact layer and removing the surrogate substrate.

FIG. 2A represents a six-junction solar cell utilizing three metamorphic layers, after an initial stage of manufacturing, which corresponds to FIG. 4 of EP 2610924, including the deposition of specific semiconductor layers on a growth substrate. 1 is a cross-sectional view of a solar cell according to an embodiment of the present disclosure.

FIG. 2B represents a five-junction solar cell utilizing two metamorphic layers after the initial stage of manufacturing, which corresponds to FIG. 3B of EP 2610924, including the deposition of specific semiconductor layers on a growth substrate. 1 is a cross-sectional view of a solar cell according to an embodiment of the present disclosure.

FIG. 2C corresponds to FIG. 3C of European Patent Publication No. 2610924, showing another five-junction solar cell utilizing two metamorphic layers after an initial stage of manufacturing, including the deposition of specific semiconductor layers on a growth substrate. FIG. 3B is a cross-sectional view of an embodiment of a solar cell of the present disclosure representing the embodiment of FIG.

FIG. 2D depicts a five-junction solar cell utilizing one metamorphic layer after the initial stages of manufacturing, including the deposition of certain semiconductor layers on a growth substrate, corresponding to FIG. 5 of EP-A-2610924. 1 is a cross-sectional view of a solar cell according to an embodiment of the present disclosure.

FIG. 2E depicts a six-junction solar cell utilizing two metamorphic layers after an early stage of manufacturing, which corresponds to FIG. 6 of EP 2610924, including the deposition of a particular semiconductor layer on a growth substrate. 1 is a cross-sectional view of a solar cell according to an embodiment of the present disclosure.

Although details of the structure of FIG. 2A will be described below, details of FIGS. 2B, 2C, 2D, and 2E are similar and will be omitted for brevity.

In particular, FIG. 2A represents the sequential formation of six subcells A, B, C, D, E and F on a GaAs growth substrate. The series of layers 302-314b grown on the growth substrate are similar to layers 102-122b discussed in connection with FIG. 3A of EP 2610924, but for clarity of this description. The description of such layers with new reference numbers will be repeated here.

Substrate 301 is specifically shown and is preferably gallium arsenide (GaAs), but could also be germanium (Ge) or another suitable material. For GaAs, the substrate is preferably a 15 degree off-cut substrate, that is, its surface is (more fully described in U.S. patent application Ser. No. 12/047,944 filed Mar. 13, 2008). It is oriented 15 degrees from the (100) plane to the (111)A plane.

In the case of a Ge substrate, a nucleation layer (not shown) is deposited directly on the substrate 301. A buffer layer 302 and an etch stop layer 303 are further deposited on the substrate or on the nucleation layer (for Ge substrates). In the case of a GaAs substrate, buffer layer 302 is preferably GaAs. In the case of a Ge substrate, the buffer layer 302 is preferably GaInAs. Thereafter, a GaAs contact layer 304 is deposited on layer 303 and an AlInP window layer 305 is deposited on the contact layer. Subcell A, consisting of the n+ emitter layers 306a and 306b and the p-type base layer 307, which will be the upper first solar subcell of the structure, is then epitaxially deposited on the window layer 305. Subcell A is generally lattice matched to growth substrate 301.

It should be noted that the structure of the multi-junction solar cell can be formed by any suitable combination of groups III-V listed in the Periodic Table, subject to the requirements of lattice constant and band gap. .. Here, the group III includes boron (B), aluminum (Al), gallium (Ga), indium (In), and thallium (T). Group IV includes carbon (C), silicon (Si), germanium (Ge), and tin (Sn). Group V includes nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi).

In one embodiment, the emitter layer is composed of AlGaInP and the base layer 307 is composed of AlGaInP, thus the p/n junction of this subcell is a homojunction. In particular, the emitter layer is composed of two regions, an n+ type emitter region 306a directly grown on the window layer 305 and an n type emitter region 306b directly grown on the emitter region 306a. The doping profiles of the different emitter regions 306a and 306b and the base layer 307 according to the present disclosure are described in EP 2610924 in conjunction with FIG. 20 thereof.

In some embodiments, a spacer layer 306c composed of AlGaInP that is not intentionally doped is then grown directly on the n-type emitter region 306b.

A base layer 307 made of AlGaInP is grown on the spacer layer 306c.

In some embodiments, the base layer 307 has a bandgap of 1.92 eV or greater.

In some embodiments, the base band gap of the first upper solar subcell is 2.05 eV or greater.

In some embodiments, the emitter of the upper first solar subcell has a first region with a doping graded from 3×10 ¹⁸ free carriers/cm ³ to 1×10 ¹⁸ free carriers/cm ³ , and directly on the first region. And a second region whose doping is constant at 1×10 ¹⁷ free carriers/cm ³ .

In some embodiments, the first region of the emitter of the upper first solar subcell is immediately adjacent to the window layer.

In some embodiments, the emitter of the upper first solar subcell has a thickness of 80 nm.

In some embodiments, the base of the upper first solar subcell has a thickness less than 400 nm.

In some embodiments, the base of the upper first solar subcell has a thickness of 260 nm.

In some embodiments, the emitter portion of the upper first solar subcell has a first region with a graded doping and a second region with a constant doping and disposed directly on the first region.

Subcell A will ultimately become the "top" subcell of the inverted deformed structure after completion of the process steps according to the invention described below.

A back field (“BSF”) layer 308, preferably p+AlInP, is deposited on top of the base layer 307 and is used to reduce recombination losses.

The BSF layer 308 drives minority carriers out of the region near the base/BSF interface to minimize the effects of recombination loss. In other words, BSF layer 308 reduces recombination losses at the backside of solar subcell A, thereby reducing recombination at the base.

Deposited on top of BSF layer 308 is a series of heavily doped p- and n-type layers 309a and 309b, which form a tunnel diode, an ohmic circuit element that forms the electrical connection between subcell A and subcell B. To do. Layer 309a may be composed of p++AlGaAs and layer 309b may be composed of n++GaInP.

A window layer 310 is deposited on top of the tunnel diode layer 309, preferably n+AlInP. The window layer 310 used in subcell B also acts to reduce interfacial recombination loss. It will be apparent to those skilled in the art that additional layers can be added or removed from the cell structure without departing from the scope of this disclosure.

On top of the window layer 310, the subcell B layer, the n+ type emitter layer 311 and the p type base layer 312 are deposited. The layers are preferably AlGaAs and AlGaAs, respectively, but other suitable materials consistent with lattice constant and bandgap requirements can be used as well. Thus, the subcell B may be composed of an emitter region of GaAs, GaInP, GaInAs, GaAsSb, or GaInAsN and a base region of GaAs, GaInAs, GaAsSb, or GaInAsN. The doping profile of layers 311 and 312 can be as described therein, in conjunction with FIG. 20B of EP 2610924.

A BSF layer 313 having the same function as the BSF layer 308 is deposited on the cell B. P++/n++ tunnel diode layers 314a and 314b, respectively, are deposited on BSF layer 308 in the same manner as layers 309a and 309b to form ohmic circuit elements to connect subcell B to subcell C. Layer 314a may be composed of p++AlGaAs and layer 314b may be composed of n++GaInP.

A window layer 315, preferably composed of n+ type GaInP, is then deposited over the tunnel diode layers 314a/314b. This window layer acts to reduce interfacial recombination loss in subcell "C". It will be apparent to those skilled in the art that additional layers can be added or removed from the cell structure without departing from the scope of this disclosure.

On top of the window layer 315, the subcell C layer, the n+ emitter layer 316 and the p-type base layer 317 are deposited. These layers are preferably n+ type GaInP and p+ type GaAs, respectively, although other suitable materials consistent with lattice constant and bandgap requirements can be used as well. The doping profile of layers 316 and 317 can be as described in connection with FIG. 20B of EP 2610924.

A BSF layer 318, preferably composed of AlGaAs, is then deposited on top of cell C, which BSF layer performs the same function as BSF layers 308 and 313.

P++/n++ tunnel diode layers 319a and 319b are deposited on BSF layer 318, respectively, similarly to layers 314a and 314b, forming ohmic circuit elements to connect subcell C to subcell D. Layer 319a may preferably be composed of p++AlGaAs and layer 319b may be composed of n++GaAs.

In some embodiments, barrier layer 320 is preferably composed of n-type GaInP and is deposited on tunnel diodes 319a/319b to a thickness of about 0.5 μm. It is intended that such barrier layers prevent threading dislocations from propagating into top and middle subcells A, B and C in opposite directions of growth or into subcell D in the direction of growth. , Co-pending US patent application Ser. No. 11/860,183, filed Sep. 24, 2007.

A first metamorphic layer (or compositionally graded intermediate layer) 321 is deposited on the barrier layer 320. Layer 321 preferably comprises a monotonically changing lattice constant, preferably compositionally, so as to achieve a gradual transition of the lattice constant from subcell C to cell D in the semiconductor structure while minimizing the occurrence of threading dislocations. It is a series of AlGaInAs layers with a stepwise slope. The band gap of layer 321 is constant over its thickness and is preferably equal to approximately 1.6 eV. One embodiment of the compositionally graded intermediate layer can also be described as being composed of (In _x Ga _1-x ) _y Al _1-y As, but the intermediate layer bandgap is constant at approximately 1.6 eV. Select x and y so that

In one embodiment of the present disclosure, an optional second barrier layer 322 can be deposited on the AlGaInAs metamorphic layer 321. The second barrier layer 322 will normally have a different composition than the barrier layer 320 and essentially performs the same function of blocking the propagation of threading dislocations. In one embodiment, the barrier layer 322 is n+ type GaInP.

A window layer 323, preferably composed of n+ type GaInP, is then deposited on the second barrier layer. This window layer acts to reduce the recombination loss in the fourth subcell "D". It will be apparent to those skilled in the art that additional layers can be added or removed from the cell structure without departing from the scope of this disclosure.

A layer of the cell D, an n+ emitter layer 324 and a p-type base layer 325 are deposited on the window layer 323. These layers are preferably n+-type GaInAs and p-type GaInAs, respectively, although other suitable materials consistent with lattice constant and bandgap requirements can be used as well. The doping profiles of layers 324 and 325 are as described in connection with FIG. 20B of EP 2610924.

A BSF layer 326, preferably composed of p+ type AlGaInAs, is then deposited on top of cell D, which BSF layer performs the same function as BSF layers 308, 313, and 318. P++/n++ tunnel diode layers 327a and 327b are respectively deposited on the BSF layer 326 in the same manner as layers 309a/309b and 319a/319b, forming ohmic circuit elements to connect subcell D to subcell E. Layer 327a is preferably composed of p++AlGaInAs and layer 327b is preferably composed of n++GaInP.

In some embodiments, the barrier layer 328 is preferably composed of n-type GaInP and is deposited on the tunnel diodes 327a/327b to a thickness of about 0.5 μm. Such barrier layers are intended to prevent propagation of threading dislocations into B, C and D of middle subcells in the opposite direction of growth or into subcell E in the direction of growth, 2007. See co-pending US patent application Ser. No. 11/860,183, filed Sep. 24, with details.

A second metamorphic layer (or compositionally graded intermediate layer) 329 is deposited on the barrier layer 328. Layer 329 preferably comprises a monotonically changing lattice constant, preferably compositionally, so as to achieve a gradual transition of the lattice constant from subcell D to subcell E in the semiconductor structure while minimizing the occurrence of threading dislocations. It is a series of AlGaInAs layers with a stepwise slope. In some embodiments, the band gap of layer 329 is approximately 1.6 eV and is constant throughout its thickness. One embodiment of the compositionally graded intermediate layer can also be described as being composed of (In _x Ga _1-x ) _y Al _1-y As, but the intermediate layer bandgap is constant at approximately 1.6 eV. Select x and y so that

In one embodiment of the present disclosure, an optional second barrier layer 330 can be deposited on the AlGaInAs metamorphic layer 329. The second barrier layer will typically have a different composition than the barrier layer 328 and essentially performs the same function of blocking the propagation of threading dislocations.

Thereafter, a window layer 331, preferably made of n+ type GaInP, is deposited on layer 330 if there is a barrier layer disposed on layer 329, and on the second metamorphic layer 329 otherwise. Deposit directly. This window layer acts to reduce the interfacial recombination loss in the fifth subcell "E". It will be apparent to those skilled in the art that additional layers can be added or removed from the cell structure without departing from the scope of this disclosure.

On the window layer 331, the layer of the cell E, the n+ emitter layer 332 and the p-type base layer 333 are deposited. These layers are preferably composed of n+ type GaInAs and p type GaInAs, respectively, although other suitable materials consistent with lattice constant and bandgap requirements can be used as well. The doping profile of layers 332 and 333 may be as described in European Patent Publication No. 2610924 in connection with FIG. 20B thereof.

A BSF layer 334, preferably composed of p+ type AlGaInAs, is then deposited on top of cell E, which BSF layer performs the same function as BSF layers 308, 313, 318, and 326.

P++/n++ tunnel diode layers 335a and 335b, respectively, are deposited on BSF layer 334 in the same manner as layers 309a/309b and 319a/319b to form ohmic circuit elements to connect subcell E to subcell F. Layer 335a is preferably composed of p++AlGaInAs and layer 335b is preferably composed of n++GaInP.

In some embodiments, the barrier layer 336 is preferably composed of n-type GaInP and is deposited on the tunnel diodes 335a/335b to a thickness of about 0.5 μm. It is intended that such barrier layers prevent threading dislocations from propagating into D and E of middle subcells in the opposite growth direction or into subcell F in the growth direction, September 2007. It is described in detail in co-pending US patent application Ser. No. 11/860,183, filed on 24th.

A third metamorphic layer (or compositionally graded intermediate layer) 337 is deposited on the barrier layer 336. Layer 337 preferably comprises a monotonically varying lattice constant, preferably compositionally, so as to achieve a gradual transition of the lattice constant from subcell E to subcell F in the semiconductor structure while minimizing the occurrence of threading dislocations. It is a series of AlGaInAs layers with a stepwise slope. In some embodiments, the band gap of layer 337 is 1.1 eV and is constant throughout its thickness. One embodiment of the compositionally graded interlayer can also be described as being composed of (In _x Ga _1-x ) _y Al _1-y As, but with a bandgap of the interlayer of approximately 1.1 eV or another. Choose x and y to remain constant with an appropriate bandgap of

In one embodiment of the present disclosure, an optional second barrier layer (not shown) can be deposited on the AlGaInAs metamorphic layer 337. The second barrier layer will typically have a different composition than the barrier layer 336 and essentially performs the same function of blocking the propagation of threading dislocations.

Thereafter, a window layer 338, preferably composed of n+ type AlGaInAs, is deposited on the second barrier layer if a barrier layer is located on layer 337, otherwise on the second metamorphic layer 337. Directly deposited on. This window layer acts to reduce the interfacial recombination loss in the sixth subcell "F". It will be apparent to those skilled in the art that additional layers can be added or removed from the cell structure without departing from the scope of this disclosure.

On top of the window layer 338, the layer of the cell F, the n+ emitter layer 339 and the p-type base layer 340 are deposited. These layers are preferably composed of n+ type GaInAs and p type GaInAs, respectively, although other suitable materials consistent with lattice constant and bandgap requirements can be used as well. The doping profile of layers 339 and 340 may be as described in European Patent Publication No. 2610924 with respect to FIG. 20B thereof.

A BSF layer 341, preferably composed of p+ type AlGaInAs, is then deposited on top of cell F, which BSF layer performs the same function as BSF layers 308, 313, 326, and 334.

Finally, a high forbidden band contact layer 342, preferably composed of p++ AlGaInAs, is deposited on the BSF layer 341.

The structure of this contact layer 342 placed on the bottom (non-illuminated) side of the photovoltaic cell with the lowest forbidden band width of the multijunction photovoltaic cell (ie, the subcell “F” in the illustrated embodiment). , And can be made to reduce the absorption of light passing through the cell, so that (i) the backside ohmic metal contact layer under the cell (non-irradiated side) also functions as a mirror layer, (ii) It is not necessary to selectively etch away this contact layer to prevent absorption.

It will be apparent to those skilled in the art that additional layers can be added or removed from the cell structure without departing from the scope of the invention.

The remaining steps in the fabrication of the multi-junction solar cell according to the illustrated embodiment include depositing a metallization on the contact layer and depositing a surrogate substrate, as shown in European Patent Publication No. 2610924, FIG. 7 and thereafter. Can be as described and shown in connection with the figure.

Although the described embodiments of the present disclosure utilize vertical stacking of 4, 5, or 6 subcells, various aspects and features of the present disclosure include fewer or more subcells, i.e., two junctions. It can be applied to a stack including cells, three-junction cells, seven-junction cells, and the like. In the case of 7 or more junction cells, 3 or more metamorphic graded interlayers may also be utilized.

Further, the disclosed embodiments are configured with top and bottom electrical contacts, but instead connect the subcells with metal contacts to the laterally conductive semiconductor layers between the subcells. You can Such an arrangement can be utilized to form 3-terminal, 4-terminal, and generally n-terminal devices. Although photogenerated current densities are usually different in different subcells, most of the available photogenerated current density in each subcell is effectively utilized to provide high efficiency for multijunction cells. These additional terminals may be used to interconnect subcells in the circuit, as provided.

Although the solar cell described in this disclosure has been illustrated and described as an example of an inverted metamorphic multijunction solar cell, various modifications and structural changes may be made without departing from the spirit of the invention. However, it is not intended to be limited to the details shown.

Therefore, while the description of semiconductor devices described in this disclosure has focused primarily on solar cells or photovoltaic devices, other optoelectronic devices such as thermophotovoltaic (TPV) cells, light receiving devices and light emitting diodes have been described. Those skilled in the art know that, with some minor changes in doping and minority carrier lifetime, they are similar to photovoltaic devices in structure, physics, and materials. For example, the light receiving element can be of the same material and structure as the photovoltaic element described above, but perhaps more lightly doped for sensitivity rather than power generation. LEDs, on the other hand, can be made of the same materials and structures, but are probably heavily doped to reduce the recombination time and thus the radiative lifetime that produces light instead of power. Therefore, the present invention also applies to light receiving devices and LEDs using the structures, material compositions, manufacturing supplies and improvements described above for photovoltaic cells.

102 buffer layer 103 etch stop layer 104 contact layer 105 window layer 106 n+ type emitter layer 107 p type base layer 108 BSF layer 109a p++ tunnel diode 109b n++ tunnel diode 110 window layer 111 n+ type emitter layer 112 p type base layer 113 BSF layer 114a p++ tunnel diode 114b n++ tunnel diode 115 barrier layer 116 transformation layer 117 barrier layer 118 window layer 119 n+ type emitter layer 120 p type base layer 121 BSF layer 122a p++ tunnel diode 122b n++ tunnel diode 123 barrier layer 124 transformation layer 125 window layer 126 n+ type emitter layer 127 p type base layer 128 BSF layer 129 p++ type contact layer 130 metal contact layer 131 adhesive layer 132 substitute substrate

Claims (9)

An upper first solar subcell (cell A) having a first forbidden band,
A second solar subcell (cell B) adjacent to the upper first solar subcell and having a second forbidden band width smaller than the first forbidden band width;
A first compositionally graded intermediate layer (116) adjacent to the second solar subcell, the first compositionally graded intermediate layer having a third forbidden band width greater than the second forbidden band width and the third forbidden band. A band width that is constant over the entire thickness of the first composition-graded intermediate layer;
Third A solar subcell (cell C) adjacent to the first composition graded interlayer, said third solar subcell having a second band gap smaller than the fourth band gap, said third solar subcell A third solar subcell, which is lattice mismatched to the second solar subcell,
Equipped with
The first compositionally graded intermediate layer has a thickness of 1.6 eV±3% over its entire thickness to achieve a gradual transition of the lattice constant in the semiconductor structure from the second solar subcell to the third solar subcell. A multi-junction solar cell characterized by having a forbidden band width. A fourth solar subcell (cell D in FIG. 1H) adjacent to the third solar subcell, the fourth solar subcell having a fifth forbidden band width smaller than the fourth forbidden band width, and the fourth solar subcell. The multijunction solar cell of claim 1, wherein the subcell further comprises a fourth solar subcell that is lattice matched to the third solar subcell. A second compositionally graded intermediate layer (124) adjacent to the third solar subcell, the second compositionally graded intermediate layer having a fifth forbidden band width greater than the fourth forbidden band width and a lattice in a semiconductor structure. The fifth forbidden band width is approximately 1.1 eV across the thickness of the second compositionally graded intermediate layer to achieve a gradual transition from the third solar subcell to the fourth solar subcell. A second compositionally graded intermediate layer that is constant;
Fourth a solar sub cell Le adjacent the second composition graded intermediate layer, fourth solar subcell having a fourth band gap smaller than the sixth band gap, the fourth solar subcell is the first A fourth solar subcell, which is lattice mismatched to the three solar subcells,
The multijunction solar cell according to claim 1, further comprising: A lower fifth solar sub cell Le adjacent to the fourth solar subcell, said lower fifth solar subcell has the sixth band gap smaller than the seventh band gap, the fifth solar subcell is the first The multijunction solar cell of claim 3, further comprising a lower fifth solar subcell that is lattice matched to the four solar subcell. A second compositionally graded intermediate layer adjacent to the fourth solar subcell, wherein the second compositionally graded intermediate layer has a sixth forbidden band width greater than the fifth forbidden band width, and the sixth forbidden band width is A second compositionally graded intermediate layer, which is constant at approximately 1.1 eV over the entire thickness of the second compositionally graded intermediate layer,
A fifth solar subcell (cell E in FIG. 2B) adjacent to the second compositionally graded intermediate layer,
A fifth solar subcell, wherein the lower fifth solar subcell has a seventh forbidden band width smaller than the fifth forbidden band width, the fifth solar subcell being lattice mismatched to the fourth solar subcell;
The multi-junction solar cell according to claim 2, further comprising: Wherein the first composition graded intermediate _{layer, (In x Ga 1-x} ) consists of _y Al _1-y As, x and y are the band gap of the first composition graded intermediate layer over the entire thickness is selected to remain constant, a 0 <x <1,0 <y < 1, the second composition graded interlayer is composed of _{(in x Ga 1-x)} y Al 1-y as , X and y are selected such that the forbidden band width of the second compositionally graded intermediate layer remains constant throughout its thickness, 0<x<1, 0<y<1. The multi-junction solar cell described in 3. An upper first solar subcell (cell A) having a first forbidden band,
A second solar subcell (cell B) adjacent to the upper first solar subcell and having a second forbidden band width smaller than the first forbidden band width;
A third solar subcell (cell C in FIG. 2D) adjacent to the second solar subcell, the third solar subcell having a third forbidden band width smaller than the second forbidden band width, and the third solar subcell. A third solar subcell, the subcell being lattice matched to the second solar subcell;
A first compositionally graded intermediate layer (521) adjacent to the third solar subcell, the first compositionally graded intermediate layer having a fourth forbidden band width greater than the third forbidden band width; A band width that is constant over the entire thickness of the first composition-graded intermediate layer;
A fourth solar subcell (cell D in FIG. 2D) adjacent to the first compositionally graded intermediate layer, the fourth solar subcell having a fourth forbidden band width less than the third forbidden band width. A fourth solar subcell, the fourth solar subcell being lattice mismatched to the third solar subcell;
A fifth solar subcell (cell E in FIG. 2D) adjacent to the fourth solar subcell, the fifth solar subcell having a sixth forbidden band width less than the fifth forbidden band width, and the fifth solar subcell. A fifth solar subcell, the subcell being lattice matched to the fourth solar subcell;
A second compositionally graded intermediate layer adjacent to the fifth solar subcell, wherein the second compositionally graded intermediate layer has a seventh forbidden band width greater than the sixth forbidden band width, and the seventh forbidden band width is A second composition gradient intermediate layer, which is constant over the entire thickness of the second composition gradient intermediate layer;
A sixth solar subcell (cell F in FIG. 2D) adjacent to the second compositionally graded intermediate layer, the sixth solar subcell having an eighth forbidden band width smaller than the sixth forbidden band width, A sixth solar subcell, which is lattice mismatched to the fourth solar subcell, and a sixth solar subcell,
Equipped with
The multi-junction solar cell, wherein the first compositionally graded intermediate layer has a forbidden band width of 1.6 eV±3% over the entire thickness of the first compositionally graded intermediate layer. An upper first solar subcell (cell A) having a first forbidden band,
A second solar subcell (cell B) adjacent to the upper first solar subcell and having a second forbidden band width smaller than the first forbidden band width;
A third solar subcell (cell C in FIG. 2E) adjacent to the second solar subcell, the third solar subcell having a third forbidden band width smaller than the second forbidden band width, and the third solar subcell. A third solar subcell, the subcell being lattice matched to the second solar subcell;
A first compositionally graded intermediate layer (321) adjacent to the third solar subcell, the first compositionally graded intermediate layer having a fourth forbidden band width greater than the third forbidden band width, and the fourth forbidden band. A first composition gradient intermediate layer having a constant band width over the entire thickness of the first composition gradient intermediate layer;
A fourth solar subcell (cell D in FIG. 2E) adjacent to the first composition graded intermediate layer, the fourth solar subcell having a fourth forbidden band width less than the third forbidden band width, A fourth solar subcell, the fourth solar subcell being lattice mismatched to the third solar subcell;
A second composition graded intermediate layer (329) adjacent to the fourth solar subcell, the second composition graded intermediate layer having a sixth forbidden band width greater than the fifth forbidden band width, and a lattice in a semiconductor structure. A second composition gradient, wherein the sixth forbidden band width is constant throughout the thickness of the two composition gradient intermediate layer so as to achieve a gradual transition of the constant from the fourth solar subcell to the fifth solar subcell. The middle layer,
A fifth solar subcell (cell E in FIG. 2E) adjacent to the second compositionally graded intermediate layer, the fifth solar subcell having a seventh forbidden band width less than the fifth forbidden band width, A fifth solar subcell, the fifth solar subcell being lattice mismatched to the fourth solar subcell;
A third compositionally graded intermediate layer (337) adjacent to the fifth solar subcell, wherein the third compositionally graded intermediate layer has an eighth forbidden band width greater than the seventh forbidden band width, and the eighth forbidden band. A third composition gradient intermediate layer having a band width that is constant over the entire thickness of the third composition gradient intermediate layer;
A sixth solar subcell (cell F in FIG. 2E) adjacent to the third compositionally graded intermediate layer, wherein the sixth solar subcell has a ninth forbidden band width that is less than the seventh forbidden band width. A sixth solar subcell, which is lattice mismatched to the fifth solar subcell, and a sixth solar subcell,
Equipped with
In order to achieve a gradual transition of the lattice constant in the semiconductor structure from the third solar subcell to the fourth solar subcell, the first compositionally graded intermediate layer has a 1.6 eV±3% forbidden thickness over its thickness. A multi-junction solar cell characterized by having a band width. A method of manufacturing a solar cell,
Preparing a first substrate (101),
Forming an upper first solar subcell (cell A) having a first forbidden band width on the first substrate;
Forming a second solar subcell (cell B) having a second forbidden band width smaller than the first forbidden band width on the upper first solar subcell;
Forming a first compositionally graded intermediate layer (116) adjacent to the second solar subcell, the first compositionally graded intermediate layer having a third forbidden band width greater than the second forbidden band width. Forming a first compositionally graded intermediate layer, wherein the third forbidden band width is constant throughout the thickness of the first compositionally graded intermediate layer;
Forming a third solar subcell (cell C) adjacent to the first compositionally graded intermediate layer, the third solar subcell having a fourth forbidden band width smaller than the second forbidden band width; Forming a third solar subcell, wherein the third solar subcell is lattice mismatched to the second solar subcell;
Forming a second compositionally graded intermediate layer (124) adjacent to the third solar subcell, the second compositionally graded intermediate layer having a fifth forbidden band width greater than the fourth forbidden band width. Forming a second compositionally graded intermediate layer, wherein the fifth forbidden band width is constant at approximately 1.1 eV throughout the thickness of the second compositionally graded intermediate layer;
Forming a lower fourth solar subcell (cell D) adjacent to the second composition graded intermediate layer, the lower fourth solar subcell having a sixth forbidden band width smaller than the fourth forbidden band width. Forming a lower fourth solar subcell, the fourth solar subcell being lattice mismatched to the third solar subcell.
Attaching a surrogate substrate (132) to the top of the fourth solar subcell;
Removing the first substrate (101),
Including,
In order to achieve a gradual transition of the lattice constant in the semiconductor structure from the second solar subcell to the third solar subcell, the first compositionally graded intermediate layer has a 1.6 eV±3% forbidden thickness over its thickness. A method for manufacturing a solar cell, which has a band width.

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